THE EGG OF THE DOMESTIC CAT 157 



In fertilization stages the pronuclei are seen with difficulty or 

 not at all. 



The preserved egg. The section of an egg at the end of the period 

 of growth show^s a granular outer zone and an inner mass some- 

 what eccentrically placed, containing many vacuoles, from which 

 the nutritive material has been dissolved by the treatment to 

 which it has been subjected. In preserved material the germinal 

 vesicle occupies a position at the periphery, entirely independent 

 of the distribution of the yolk material within the egg. It may 

 lie either in the clear protoplasm at the one pole of the egg, or 

 at the opposite pole, where the nutritive globules are accumulated 

 most abundantly, or at any intermediate point. 



In germinal vesicles at this stage, one frequently finds the 

 chromatin gathered together in a number of compact spheres of 

 variable size, which on the whole are inclined to lie near the 

 nuclear membrane. Holl ('93) has given a description of the 

 nuclear changes during which these bodies appear in the mouse 

 egg. He would have them originate in the nucleus from cor- 

 puscles of Schroen and migrate thence into the nuclear sap. 

 He notes incidentally that the reticulum of the nucleus disappears 

 entirely. Although this account is interesting, the condensation 

 of the chromatin network in whole or in part seems sufficient to 

 account for the origin of the spheres in question. These vary in 

 number from about 35 to 10, the latter number apparently rep- 

 resenting the more advanced stage of development and standing 

 just before the organization of the spindle. 



In preserved material, the contour of the nucleus in a mature 

 egg is usually irregular, but the condition of the cytoplasm about 

 it generally suggests that the lobulated or rugose state is due 

 to shrinkage, i.e., imperfect preservation. Van der Stricht ('09) 

 considers an apparently similar phenomenon in the bat normal, 

 and coupled with very late stages of the growth of the egg. It is 

 to be noted that this form of the nucleus may be, and undoubtedly 

 is, artificial and still indicate a special condition within, i.e., 

 very dilute nuclear sap, which is as fundamental a difference as 

 would be a variation from its preceding spherical shape. 



